Field
The present invention relates to an optical module for optical communication provided with an APD (avalanche photodiode).
Background Conventional optical modules include a resistor connected between a power supply terminal and a cathode of an APD and a cathode of a surge preventing Zener diode connected to a connection point between the resistor and the cathode of the APD (e.g., see Japanese Patent Laid-Open No. 11-275755).
When a surge is inputted, if a cathode voltage of the APD is less than a breakdown voltage of the Zener diode, a surge current flows through the APD, not the Zener diode. When strong light is made incident on the APD, a voltage drop of the resistor causes the cathode voltage of the APD to decrease, and a difference from the breakdown voltage of the Zener diode expands, resulting in a problem that a surge current is more likely to flow through the APD.